>Unsafe in rust means you are skirting guarantees given by the language. It doesn't mean the code will blow up when run. It's just an explicit way to tell the compiler you are operating at your own risk.

I'm fully aware of this. That's why I put 'unsafe' in quotes.

However, it's surely fair to point out that you can't implement doubly linked lists or mutable iterators in Rust without giving up Rust's usual guarantee of memory safety. If this guarantee is not actually that big of a deal, as you appear to be suggesting, then why all the hype about it from Rust advocates?

>The question was show us a case where the borrow checker was wrong.

No, that was not the question. OP just asked for 'rejected code that should work perfectly fine'. There are of course loads of examples of such code. Perhaps the simplest is the case of mutable iterators that I mentioned. A correctly implemented mutable iterator is perfectly safe, but rejected by Rust's borrow checker unless certain parts of the implementation are marked unsafe.